A dust swarm detected after the main Leonid meteor shower in 1998

The Leonid meteor shower in November 1998 was widely observed by both visible and radio astronomers. A significant outburst, which included several fireballs, was observed on the morning of Nov. 17, about 16 hours before the predicted maximum of the main shower. The main shower was also observed as expected on Nov. 18 and many observations of both these events have been recorded. About 18 hours after the main shower, an abnormal peak of the ionosphere characteristic value f(b)E(s) was detected by two separate ionosphere observational stations, Guangzhou and Hainan. The very high f(b)E(s) value was maintained over one hour. The most likely explanation for this abnormally high activity is that the ionosphere was bombarded by a swarm of dust particles, much smaller than those which produce a visible or radio trail. The near coincidence in time between this event and the Leonid shower strongly suggests that we should look for an explanation for this dust swarm in terms of the dynamics and evolution of the Leonid meteoroid stream and this paper explores these aspects.